Already today cellular mobile phone devices may support a plurality of different radio access technologies (RATs) in order to automatically select a RAT to provide services to the user, to enable the user to select one of these RATs for providing its services or to autonomously fall back to another RAT in case missing coverage by the currently selected RAT. An example for such a type of cellular mobile phone device is a conventional dual-mode cellular mobile phone device supporting Global System for Mobile Communication (GSM)/(Enhanced) General Packet Radio Service ((E)GPRS) and Universal Mobile Telecommunications System (UMTS). In future, e.g. with the deployment of Long Term Evolution (LTE) evolved UMTS Radio Access Network (eUTRAN), even triple-mode cellular mobile phone device will become more and more common.
For a cellular mobile radio communication system implementing a certain radio access technology, several frequency bands may be standardized and allocated for each radio access technology. By way of example, for GSM, possible frequency bands are GSM 850, GSM 900, GSM 1800, GSM 1900. Furthermore, for UMTS, possible frequency bands are Band I (2100), Band II (1900), Band III (1800), Band IV (2100), Band V (850), Band VI (850), and Band VII (2600) and others.
During an initial radio cell search (or during another type of a global radio cell search), a multi-mode, multi-band mobile radio phone usually scans all possible and supported frequency bands of all supported RATs for radio cell carriers in order to decide which radio cell shall be selected, i.e. on which radio cell the subscriber should camp.
Obviously, the time needed for such a radio cell search increases with the number of supported RATs and frequency bands. And it shall be pointed out that this time will also be noted by the user of the mobile radio phone device as the time until he is able to use cellular services via his mobile radio phone device.